Centrifugal mill with wind sifter



Sept. 25, 1962 H. MUND CENTRIFUGAL MILL WITH WIND SIFTER 2 Sheets-Sheet 1 Filed June 5, 1961 HEINRICH MUND S UJI e mm FO 1U It A s1 BWM 3 BmJbdW,

Sept. 25, 1962 H. MUND CENIRIFUGAL MILL WITH WIND SIFTER File June 5, 1961 2 Sheets-Sheet 2 )Emu/,vijand AUnited States Patent O CENTRIFUGAL MILL WITH WIND SIF'IER Heinrich Mund, Springe, Deister, Germany, assigner to Metallwerk Bahre K.G., Springe, Deister, Germany, a

firm of Germany Filed June 5, 1961, Ser. No. 114,882 Claims priority, application Germany June 11, 1960 Claims. (Cl. 241-49) The present invention relates to a centrifugal mill which is provided with a Wind sifter yfor preparing the chips for producing chip board with gradually blended layers.

For the proper preparation of the chips for the production of chip board with gradually lblended layers it is of great importance to form a mixture which is sumciently segregated into coarser and liner chips and which is thereafter treated with glue or adhesive and formed into boards.

In the art of producing chip iboard, there have been prior disclosures of centrifugal mills for the further sizereduction of the Wood chips which are supplied by a chipproducing machine. These centrifugal mills are equipped with screens of the same aperture lsize and therefore only produce chips of substantially the same size. When these known mills were used for producing the conventional three-ply board, in which the two outer layers consist of fine chips and the central layer of coarser chips, it

`was necessary to produce two different grades of chips which could not be done at the same time by the same centrifugal mill.

It is an object of the present invention to provide a centrifugal mill which is capable of producing a mixture of wood chips in which the coarse and iine chips are extensively segregated and which obviates the previous necessity of providing separate centrifugal mills for producing chips of different sizes.

For attaining this object, the invention consists in providing the centrifugal mill with screens of different aperture sizes and in subjecting the chip material which is to be further reduced in size to a wind-sifting treatment while falling from a hopper toward the screens. The screens with a larger aperture size are thus supplied primarily with coarser chips, While the screens with a smaller aperture lsize are supplied primarily with chips of a smaller size. The coarser chips which are then treated by the largesize screen or screens are then broken up only slightly and may thereafter -be used for forming a solidifying wooden framework or base within the cent1-al part of the chip board While a part of the finer chips are broken up further by the finer screens to such an extent that the outer layers of the chip board will have a structure which insures that the chips board will have uniform, line-particle, and smooth outer surfaces.

A further feature of the invention consists in providing the chamber of the centrifugal mill above the screens with horizontally directed air inlet openings and the opposite wall of the chamber with adjustable air outlet openings which lead to an air-collecting channel which is connected to the suction intake of a fan. It is thus possible to adjust the centrifugal mill in accordance with the particular composition ofthe chip material. A further advantage which is thus attained is that the same air current which is used for conveying the chip material may also be used for sifting the material in the centrifugal mill.

According to one preferred embodiment of the invention, the centrifugal mill is also provided near the lower end of its chamber and substantially perpendicularly underneath the -feed hopper with an opening leading toward 3,055,597 Patented Sept. 25, 1962 the outside. By this arrangement it is possible to segregate chips of too large a size as well as foreign bodies, such as rocks, gravel, metal pieces, and the like from the chip material before the same passes to the beater and screens of the mill. The different screens of the mill are also exchangeable and may thus be provided in accordance with the particular types of wood to be worked upon and in accordance with the desired chip sizes and the type and quality of the chip boar-d to be produced.

The objects, features, and advantages of the present invention Will become more clearly apparent from the following detailed description thereof which is to be read With reference to the accompanying diagrammatical drawings, in which:

FIGURE 1 `shows a side view of the centrifugal mill according to the invention and of the associated fan; while FIGURE 2 shows a front view, partly in section, of the centrifugal mill a-s seen in the direction of the arrow II in FIGURE 1.

Referring to the drawings, the chip material to be treated is fed to the centrifugal mill by means of a conveyor belt 3 from which it drops through feed hopper 4 into a chamber 5 into which an air current enters from one side in a substantially horizontal direction. The front part 6 of chamber 5 is equipped with parallel vertical guide plates 7 which exert a directing effect upon the air current. 'I'he opposite Wall 8 of chamber 5 is provided with air outlet openings which are adjustable by means of shutter plates 9. From these outlet openings the air passes into a channel 10 Which is connected through a pipe 11 to the suction intake of a fan 12.

The beater 18 of the centrifugal mill is of a conventional construction except that the screens 13, 14, and 15 have different aperture sizes. These screen are arranged in such a manner that screen 13 with the largest aperture size is located closest to the vertical plane which extends through funnel 4, that is, farthest toward the left, as seen in FIGURE 1. The screens with progressively smaller aperture sizes are then located in the direction of the air current and screen 15 With the finest aperture size is located farthest toward the right, that is, most remote from the air inlet 6. Consequently, the coarser chips which are least exposed to the horizontal current are driven through screen 13 with the largest aperture size, while the finer chips which are taken along by the horizontal air current for the greatest distance pass through screen 15 with the smallest aperture size. The greatest part of the chips, that is, of the coarse as well as of the fine chips, is subjected to a further size reduction by screens 13, 14, and 15. However, this screen arrangement also prevents the desired coarser chips from being broken up too much. The result of the entire arrangement is that the chip material is segregated to the desired sizes.

The mill according to the invention may be further provided with an adjustable flap 16, as indicated in FIG- URE 1 in dot-anddash lines which may be adjusted to different positions to eliminate from chamber 5 through an outlet 17 any foreign bodies, gravel, metal parts, and the like as Well as chips which are too large. A control flap 19 in channel 10 may also be adjusted to different positions for regmlating the air current passing through chamber 5 in accordance with the most suitable operating conditions.

Although the invention has been illustrated and described With reference to the .preferred embodiments thereof, it should be understood that it is in no Way limited to the details of such embodiments but is capable of numerous modifications within the scope of the appended claims.

The invention having now been fully disclosed, what is claimed is:

1. A centrifugal mill comprising a chamber having side walls and one substantially open side forming an air inlet, an open lower end, and air-outlet apertures in the side wall opposite to said inlet, a feed hopper at the upper end of said chamber within a plane near said inlet side for passing a loose chip material into said chamber, means for passing an air current through said inlet, said chamber, and said outlet apertures for sifting the material falling from said hopper into larger and smaller chips so that the larger chips will move downwardly within an area of said chamber near said inlet and the smaller chips will move downwardly Within areas more remote from said inlet, a centrifugal beater underneath the open lower end of said chamber and adapted to receive the chips falling through said chamber and a plurality of screens having different aperture sizes at least partly surrounding said beater, the screen having the largest aperture size being disposed underneath said area near said inlet and adapted to receive the larger chips from said chamber, and the screen having the smallest aperture size being disposed underneath the area most remote from said inlet and adapted to receive the smallest chips from said chamber.

2. A centrifugal mill comprising a chamber having side walls, an open lower end, substantially horizontally extending air inlet openings in a first of said side walls, and air outlet openings in the opposite side wall, an aircollecting channel connected to said outlet openings, a feed hopper at the upper end of said chamber within a plane near said first side wall for passing a loose chip material into said chamber, a suction fan connected to said collecting channel for drawing an air current through said inlet openings, said chamber, and said outlet openings for sifting the material falling from said hopper into larger and smaller chips so that the larger chips will move downwardly within an area of said chamber near said inlet openings and the smaller chips will move downwardly within areas more remote from said inlet openings, a centrifugal beater underneath the open lower end of said chamber and adapted to receive all of said chips falling through said chamber, a plurality of screens having different aperture sizes at least partly surrounding said beater, the screen having the largest aperture size being disposed underneath said area near said inlet openings and adapted to receive the larger chips from said chamber, and the screen having the smallest aperture size being disposed underneath the area most remote from said inlet openings and adapted to receive the smallest chips from said chamber, and a container also connected to said suction fan for receiving the chips passed through said screens.

3. A centrifugal mill as deiined in claim l, further comprising means for adjusting the size of said outlet apertures.

4. A centrifugal mill as defined in claim 2, further comprising means Within said collecting channel for controlling the air current passing therethrough to said suction fan.

5. A centrifugal mill as delined in claim 1, in which' said mill chamber has an outlet near its lower end at a point above said screens and substantially perpendicularly underneath said feed hopper 'for discharging foreign bodies and chips of too large a size from said chamber.

References Cited in the le of this patent UNITED STATES PATENTS 775,004 Freid Nov. l5, 1904 1,834,981 Stebbins Dec. 8, 1921 2,367,179 Arnold Jan. 16, 1945 2,764,361 Moore Sept. 25, 1956 

